At least three people were killed and dozens injured as the two camps battled each other around street barricades with stone-throwing and in some cases gunfire. Black smoke poured into the sky over Beirut from burning roadblocks.

The fighting quickly took on a dangerous sectarian tone in a country whose divided communities fought a bloody 1975-1990 civil war. Gunmen from neighboring districts in the northern city of Tripoli - one largely Sunni Muslim, the other largely Alawites, a Shiite Muslim offshoot - fought each other, causing two of the fatalities.

The day gave a frightening glimpse of how quickly the confrontation between Saniora's government and the Iranian-backed Hezbollah and its allies could spiral out of control, enflame tensions among Sunnis, Shiites and Christians and throw Lebanon into deeper turmoil.

In the evening, the opposition announced it would call off the roadblocks and the nationwide general strike that sparked the unrest, saying it had delivered a warning to the government. But it threatened more protests.

Suleiman Franjieh, a Christian opposition leader, told Hezbollah's Al-Manar TV the next steps "will be nothing compared to what we saw today" if the government does not respond to the opposition's demands.